1. Field of the Invention
The present invention relates to a technology for relaying communication between bases in a wide area network.
2. Description of the Related Art
It is a common practice to construct a wide area Ethernet (registered trademark), which is a kind of a Wide Area Network (WAN), by using each of Local Area Networks (LANs) in an Ethernet as a base and connecting the bases with one another. One method for connecting the bases with one another is to connect the plurality of LANs to one communication relaying apparatus and to realize a full-mesh connection within the communication relaying apparatus. By using this method, it is possible to construct a full-mesh Ethernet network with a simply configuration.
In such a communication relaying apparatus, there is a possibility that, when packets that have been input from a plurality of bases have congestion, some of the packets may be discarded, and thus the quality of communication can degrade. To cope with this problem, as disclosed in Japanese Patent Application Laid-open No. 2002-64540, for example, a communication relaying apparatus that guarantees the minimum bands for the bases from which the packets are input and limits the traffic that can cause congestion within the communication relaying apparatus, so as to assure scalability of the Ethernet network has been proposed.
However, according to the conventional technique, disclosed in Japanese Patent Application Laid-open No. 2002-64540, a multipoint unit that is operable to switch and output traffic addressed to different bases is configured so that the traffic having been input thereto is switched regardless of the minimum band guaranteed for each of the bases. Thus, in sometime, traffic addressed to one of the bases can be occupied by traffic coming from another one of the bases that has a higher input traffic band. Consequently, there is a possibility that the occupancy tendency in the traffic becomes imbalance in the communication between the bases.
One example of a method for assuring a band for the communication between the bases is to append a virtual Local Area Network (VLAN) tag to each packet at each of the bases. According to this method, each packet is identified with a VLAN tag value so that a band is assigned to each of the bases on the output side. This method, however, has a problem because the VLAN tag appended to each packet makes the overhead of the packet larger and makes the band available to a user smaller. Also, another problem is that a user terminal is required to have a function of appending a VLAN tag to each packet, and the user is not able to use the appended VLAN tag freely.